>>> import arcpy
>>> mxd = arcpy.mapping.MapDocument(r"CURRENT")
>>> arcpy.mapping.ExportToPNG(mxd, r"Z:\test\test2.png", "PAGE_LAYOUT", 1600, 2400, 400)
Maybe issue can be easy one but i've no clue for now.
The code above work perfectle as

but when i try outside from mapdoc from file as below i'm losing annotations. Labels seems fine. Any idea for this behaviour? Any idea for source of difference ?
import arcpy
mxd = arcpy.mapping.MapDocument(r"Z:\test\test.mxd")
arcpy.mapping.ExportToPNG(mxd, r"Z:\test\test.png", "PAGE_LAYOUT", 1600, 2400, 400)
